In the D. J. Foote U.S. Pat. No. 3,526,110 there is disclosed a trailer coupler cover lock in the form of a cover plate for lockable application to the open underside of a trailer hitch coupler to prevent unauthorized tow-away of a detached trailer through the application, by a thief, of a towing vehicle ball into the trailer hitch coupler socket. Said cover plate houses a set screw which, when adjusted, clamps a portion of a rim on the coupler socket against and under a portion of a flange on the cover plate. A lock controlled plug extension within the cover plate has a transverse bore therein, registering in one turned position of said plug extension with alined openings in the cover plate whereby an externally applied tool may engage and operate the set screw to control the blocking association as between the cover plate and the coupler socket. Thieves and tamperers, however, have developed a method of thwarting the intended tool controlled operation of said set screw. This is accomplished by the insertion of a strong flexible cord of the like into a crevice between the impinged cover plate and coupler socket and wrapping the same about an outer shank portion of the set screw. When the cord is pulled it will turn the set screw to a position which will thereby permit unauthorized disengagement of the protective cover plate from the mouth of the coupler socket. The present invention provides a construction which will prevent such unintended and unauthorized operations of the set screw by encasing the vulnerable portion of the set screw shank in a freely turnable sleeve which renders the set screw impervious to operation by a cord or tool unauthorizedly applied to an accessible portion of the shank of the set screw.
Applicant is not aware of any prior art wherein a lockable, tool manipulated set screw in the environment herein disclosed, has the outer end portion of the shank housed within a non-removable, but freely turnable sleeve.
A more specific object of the present invention is to provide, in a tamper-proof set screw assemblage for locking devices, a freely rotatable sleeve housing a portion of the set screw shank impervious to the unauthorized application of turning means thereto, capped by a non-removable, freely turnable washer which holds the sleeve on the set screw and which cannot be operated so as to transmit turning movement to the set screw.
Still further objects of the invention are to provide a tamper-proof lock-associated set screw of the character described which is simple in design and construction, which is inexpensive and easy to apply, which functions very effectively for its intended purpose, and which is strong and durable.